1. Field of the Invention
The present invention relates to a reflow apparatus preferably usable for performing reflow soldering of an electronic component to a printed circuit board.
2. Description of the Related Art
A reflow soldering apparatus includes a pre-heating unit, a main heating unit, and a cooling unit, which are accommodated in a furnace housing. The reflow soldering apparatus solders an electronic component to a printed circuit board (hereinafter, referred to as a xe2x80x9cboardxe2x80x9d or a xe2x80x9cworkpiecexe2x80x9d) or the like as follows. The electronic component is placed on a printed circuit board with solder and is transported to the inside of the furnace housing. The solder is pre-heated by the pre-heating unit, and then heated by the main heating unit to a soldering temperature so as to be melted. Then, the solder is cooled by the cooling unit.
The heating units in the reflow apparatus use, for example, hot winds, heat rays such as infrared rays, or a combination thereof.
An exemplary conventional reflow apparatus 800 of a hot wind circulation type has a structure as shown in FIG. 8. The reflow apparatus 800 operates as follows.
An air blower 54 includes a fan 52 provided below a bottom surface 7a of a board 7 carrying an electronic component to be soldered, and a motor 53 for rotating the fan 52. The air blower 54 absorbs air from the outside to the inside of the reflow apparatus 800. Then, the air circulates in the reflow apparatus 800. More specifically, the air flows in a direction of arrows A, and is heated by a heater 51 so as to become a hot wind. Then, the hot wind flows in a direction of arrows B and is blown toward a top surface 7b of the board 7. The hot wind collides into the top surface 7b, flows downward in a direction of arrows C, and is absorbed into an absorbing opening (not shown) of the fan 52.
FIG. 9 shows another conventional reflow apparatus 900 disclosed in Japanese Laid-Open Publication No. 11-192545. The reflow apparatus 900 includes a pair of fans 52 for respectively heating both a bottom surface 7a and a top surface 7b of a board 7. The reflow apparatus 900 also includes a heater 51 above the top surface 7b and another heater 51 below the bottom surface 7a. The pair of fans 52 are SIROCCO fans both rotatable about a rotation shaft 52a provided in a lower part of the inside of a furnace housing 90 and arranged parallel to the board 7 and the heaters 51. The rotation shaft 52a is driven by a motor 53 via a belt conveyor mechanism 55.
FIG. 10 shows still another conventional reflow apparatus 1000 also disclosed in Japanese Laid-Open Publication No. 11-192545. The reflow apparatus 1000 includes two air blowers 54 for respectively heating a bottom surface 7a and a top surface 7b of a board 7. The reflow apparatus 1000 includes heaters 51 respectively provided above and below the board 7, and the air blowers 54 each including a fan 52 and a motor 53.
The above-described conventional reflow apparatuses have the following problems.
The reflow apparatus 800 shown in FIG. 8 only heats the top surface 7b of the board 7. Therefore, it takes a relatively long time to uniformize the temperature of the entire board 7. Furthermore, a dispersion in the temperature of the board 7 may cause a defect in soldering.
The reflow apparatus 900 shown in FIG. 9 drives the fans 52 by the motor 53 via the belt conveyor mechanism and the rotation shaft 52a which is longer than the width of the reflow apparatus 900. Therefore, the reflow apparatus 900 has the problems of, for example, a bearing (not shown) for supporting the rotation shaft 52a having a short life and a belt of the belt conveyor mechanism needing regular replacement. These all contribute to making maintenance of the reflow apparatus 900 difficult.
The reflow apparatus 1000 shown in FIG. 10 includes two air blowers 54 respectively above and below the board 7, and therefore is unavoidably relatively large in size.
A reflow apparatus according to the present invention includes at least one heating unit. Each of the at least one heating unit includes an air blower for circulating air; a partition for defining an air circulating path; at least a first slit heater and a second slit heater for heating a workpiece with the circulating air, the workpiece having a first surface and a second surface; and a furnace housing for accommodating the workpiece. The air blower includes a first fan for blowing the air toward the first surface of the workpiece, a second fan for blowing the air toward the second surface of the workpiece, and a motor for rotating the first fan and the second fan. The first fan and the second fan are provided in correspondence with the at least first slit heater and the second slit heater.
In one embodiment of the invention, the motor has a rotation shaft provided above the workpiece in a perpendicular direction to workpiece.
In one embodiment of the invention, the first fan and the second fan have different sizes from each other.
In one embodiment of the invention, the first slit heater and the second slit heater are provided so as to interpose the workpiece therebetween. Each of the first slit heater and the second slit heater has a slit structure including a plurality of pipe heaters, each having a nickel-chrome wire coiled therein, and a plurality of flat metal plates arranged in connection with, and perpendicular to, the pipe heaters.
In one embodiment of the invention, the air circulating path defined by the partition includes a first air path for guiding the air from the first fan toward the first slit heater, a second air path for guiding the air from the second fan toward the second slit heater, and a third air path for guiding the air from the first slit heater to the first surface of the workpiece and further to the first fan and the second fan, and guiding the air from the second slit heater to the second surface of the workpiece further to the first fan and the second fan.
In one embodiment of the invention, the at least one heating unit includes a plurality of heating units, and each of a temperature of the plurality of heating units is independently adjustable.
Thus, the invention described herein makes possible the advantages of providing a compact reflow apparatus which can heat a workpiece uniformly for satisfactory soldering, has a relatively long life, and is easy to maintain.